STM Observation of Single Electron Charging in 70 nm InAs Quantum Dots

Abstract

Using electron-beam lithography and reactive ion etching, we have patterned InAs/AlSb-based double-barrier resonant tunneling structures into dots of 70 nm in diameter. The confining potential of electrons in the InAs quantum disc is abrupt and square. A scanning tunneling microscope is adopted to measure the dc current–voltage characteristics at 4.2 K, and features owing to Coulomb blockade and Coulomb staircase can be clearly identified. In addition, the current–voltage characteristics display telegraph noise due to charging and discharging of single electrons at surface states.